1. Field of Invention
The present invention relates to a mounting case accommodating an electro-optical device, such as a liquid crystal panel, which is used as a light valve of a projection display apparatus, such as a liquid crystal projector, a method to manufacture the mounting case, an electro-optical device in a mounting case, in which the electro-optical device is accommodated or encased in the mounting case, and a projection display apparatus including the electro-optical device encased in the mounting case.
2. Description of Related Art
In the related art, generally, when a liquid crystal panel is used as a light valve of a liquid crystal projector, the liquid crystal panel is not provided in an exposed state on a console, etc., constituting the liquid crystal projector, but it is accommodated or encased in a suitable mounting case. Then the mounting case including the liquid crystal panel is provided on the console. This is because the liquid crystal panel can be easily fixed or attached to the console by suitable screw holes provided in the mounting case.
In the liquid crystal projector, source light emitted from a light source is projected on the liquid crystal panel in the mounting case as focused light. Light having passed through the liquid crystal panel is magnified and projected on a screen to display images. In this way, since the magnified projection is generally predetermined in the liquid crystal projector, relatively intensive light emitted from a light source, such as a metal halide lamp is used.
However, in this construction, first, there is a problem in that the temperature of the liquid crystal panel in the mounting case, particularly of the liquid crystal panel, rises. The rise in temperature causes the rise in temperature of the liquid crystal interposed between a pair of transparent substrates in the liquid crystal panel. Therefore, the characteristics of the liquid crystal are deteriorated. In addition, when the light emitted from the source light is uneven, the liquid crystal panel is partially heated, and then the deviation of its transmittance is generated by the so-called hot spots. Thus, the quality of projected images deteriorates.
Techniques for preventing the rise in temperature of the liquid crystal panel include an approach for preventing the rise in temperature of the liquid crystal panel by providing a radiating sheet between the liquid crystal panel and a radiating plate in a liquid crystal display module including the liquid crystal panel and a package for holding and accommodating the liquid crystal panel and having the radiating plate. In addition, technology, such as reducing incidence of unnecessary infrared rays by arranging heat ray cut-off filters between light sources and a liquid crystal panel or by air-cooling or water-cooling the liquid crystal panel is known.
However, the related art approaches for preventing the rise in temperature of the liquid crystal panel have the following problems. As long as intensive light is emitted from the light source, the problem of the rise in temperature of the liquid crystal panel may occur at any time. Therefore, in order to obtain still higher image quality, more effective measures to prevent the rise in temperature are required instead of or in addition to the aforementioned approaches.
Further, in the aforementioned liquid crystal panel encased in a mounting case, the relationship between the liquid crystal panel and the mounting case also cause problems other than the problem of the rise in temperature in the liquid crystal panel itself. That is, the transparent substrate constituting a liquid crystal panel is made of, for example, quartz glass or neoceram having a relatively small coefficient of linear expansion while the mounting case is made of, for example, metals having relatively large coefficients of linear expansion. However, the mounting case may expand more than the transparent substrate even when they are radiated with the same light (energy radiation). Therefore, depending on the expansion of the mounting case, the liquid crystal panel, which is to be accommodated at a predetermined location in the mounting case, may cause dislocation. As a result, it is difficult to perform an accurate enlargement projection on a screen because the liquid crystal panel is dislocated from a focus point of light sources.
On the other hands, if attention is paid to the above-described difference between the coefficients of linear expansion, there is a problem that may occur when the liquid crystal projector is used in a low temperature atmosphere or during a cooling-off process. That is, the mounting case having a larger coefficient of linear expansion contracts more than the transparent substrate having a smaller coefficient of linear expansion. Due to this construction, the liquid crystal projector receives unnecessary force from the mounting case. As a result, an optical anisotropy may be generated in the liquid crystal panel, thereby forming irregular color on an image. Additionally, this problem frequently occurs especially when the liquid crystal projector is used in an environment of less than 10° C.